As others have said, but I'm going to repeat, first take off the bottom leaves, then put in a glass of water in the fridge. You don't want any leaves under the water (true of most things you do, like cut flowers). Where you've removed the leaves, you may get roots. Leaves under the water will just rot.

The mint issue in the garden is one to contend with. Even in pots I've had them climb out and run around.

when I have a bundle of fresh mint or basil and has to stay in the refrigerator for 2 or 3 days I take kitchen paper I wet it well with water ....and I wrap the bundle of fresh herbs with the wet kitchen paper and leave it in the fridge. It stays fresh and with good aroma up to 3 days. Never tried if it works for longer.

I would think a long time, as long as the leaves aren't underwater. You may want to take a nip at the bottom of the stems every few days if they aren't rooting, kind of what you do with a floral arrangement.

Another great use for mint (I know that isn't the question, but while we're here ...) is to buy some Near East taboule. Make as per directions, but then get lots of mint and parsley and chop. A few minutes in the morning, the afternoon in the fridge, and a great cold supper (add a can of garbanzos, some nuts, and/or some meat of choice to make it a full meal).

I'm not sure you can do this with mint, but when i have an abundance of fresh herbs, like parsley, basil, or thyme, I wash and dry them well, and then I loosely place in a tupperware and freeze. I wouldn't use the herbs as a garnish, but they are as close to fresh for cooking.

I know the leaves rot when they are partially submerged. This method actually works for basil. The leaves never rotted, but eventually turned yellow.

I gave this a try. I submerged a small mint stem with leaves on it last Tuesday and they are still fine. The little bit of flower at the end that is sticking out of the water turned black, but the rest is just fine, not slimy or rotting.

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May you live as long as you wish and love as long as you live.
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I would think a long time, as long as the leaves aren't underwater. You may want to take a nip at the bottom of the stems every few days if they aren't rooting, kind of what you do with a floral arrangement.

Is it important to leave the mint at room temperature when it's stored upright in a glass? I put it in the fridge when i bought it on Saturday, and it's not looking too good this morning. Looks wilty and parts are brown :(.

My submerged mint leaves are starting to get a bit paler. But, they still feel fresh. They have been under water in a glass on my kitchen counter since 17 July. That's nearly two weeks. The water is very minty.

__________________
May you live as long as you wish and love as long as you live.
Robert A. Heinlein

Is it important to leave the mint at room temperature when it's stored upright in a glass? I put it in the fridge when i bought it on Saturday, and it's not looking too good this morning. Looks wilty and parts are brown :(.

Did you cut a bit off the bottom stems before you put them in water? They kind of seal up when you first buy them and don't take up water. It shouldn't matter if you keep them in the fridge or on the counter.